Light include / exclude issue

[Nuno]

Hello everyone

So, I am having a bit of a issue trying to figure out how can I remove a light reflection from the floor and leave it on other objects. Let me try to explain the issue.

I am using a Image / backplate as BG and want to add a certain objects to it. In order to catch shadows and reflection into the floor I added a plane with a shadow catcher material, so far everything worked as planed.
The issue starts when I try to light the object with corona lights... I just want the lights reflection affecting the 3D added objects not the floor. I tried to exclude the reflection of the light into the floor by using the exclude tab and nothing... still appears. Tried to uncheck the seen by reflections but obviously removes it in all objects.

So basically what I wanted to know is if there is a way to remove the light reflection from the floor and not on the other objects?

Thank you,

Best

[TomG]

If I understand what you want, I think the way I'd approach it is to duplicate the CoronaLight. One would be set to Shadowcatcher illuminator, with "Visible in reflections" off, so it would cast shadows on the plane but not reflections (and no reflections on other objects either) and probably set to exclude all objects in the scene except the plane so it doesn't contribute lighting to them; now this one is simply casting shadows onto the catcher.

Then a copy of the Light, Shadowcatcher illuminator off (so now it contributes nothing to the shadowcatcher), with Reflections on, which will cast light and reflections on everything else, but not the catcher plane.

Of course, this is "not physically realistic" because in real physical terms, the light should be reflecting off the ground plane too :)

[TomG]

The above assumes you want reflections on the shadowcatcher from the *objects* in the scene, just not from this particular light source (otherwise, you can of course just make the shadowcatcher non-reflective :) )

[Nuno]

The above assumes you want reflections on the shadowcatcher from the *objects* in the scene, just not from this particular light source (otherwise, you can of course just make the shadowcatcher non-reflective :) )

Hi TomG

Thank you for your response.

I do understand that is not physical accurate, but many of my work relies on VFX compositing in live action or stills and sometimes we need to fake the physically accurate in order to achieve the best results. Sometime HDRi lighting by it self don't do the job and we need to fake lighting by adding "fake" ones to interact with cgi. Everything counts :)

I posted a dummy test file of my setup to better describe the problem I am facing. In there you will see kind of the effect I am trying to achieve, and I just cant remove the reflection from the floor (shadowcatcher also with reflection)

Thank you

Best

[Nuno]

Hi

Sorry to be so persistent on this subject.
Been testing and trying 1001 ways but, I just cant understand how the include and exclude tab work on corona light object.
I might be doing the wrong way but I am thinking like this, if I include a object into the corona light tab the only thing that should be affected should be that object right? The same will happen if I exclude, the only one affected would be the one that is not on the tab.

Is this some sort of limitation, a work in progress or just a bug?

Thank you

[TomG]

Looks like "Shadowcatcher Illuminator" is not a setting for CoronaLights in C4D at the moment, so for the suggested technique to work, you'd have to use a CoronaLightMtl instead (which does have that option). For now, CoronaLights will never reflect in a ShadowCatcher material as far as I can see from my tests.

The Includes and Excludes should work as you describe - set to Include for ObjectA, then ObjectA should be the only one affected by that light or light material; set to Exclude, then all objects except ObjectA would be affected by that light or light material. This is working as expected for me - if it is not working that way for you, could you give some steps, an example scene, and what you expect to happen that is not happening? Thanks!

[Nuno]

Looks like "Shadowcatcher Illuminator" is not a setting for CoronaLights in C4D at the moment, so for the suggested technique to work, you'd have to use a CoronaLightMtl instead (which does have that option). For now, CoronaLights will never reflect in a ShadowCatcher material as far as I can see from my tests.

The Includes and Excludes should work as you describe - set to Include for ObjectA, then ObjectA should be the only one affected by that light or light material; set to Exclude, then all objects except ObjectA would be affected by that light or light material. This is working as expected for me - if it is not working that way for you, could you give some steps, an example scene, and what you expect to happen that is not happening? Thanks!

Yes, "Shadowcatcher Illuminator" still isn't a setting for CoronaLights in C4D.
I tested that technique you described by using a plane as a light emitter / reflector with a CoronaLightMtl assign, the result is better but the reflection on the floor is still noticed.

As far I tested the include and exclude on the light are not working as expected as I always see the reflection on the floor no matter what.

I attached a c4d file with the 2 setups so that you can better see what is the problem. Just hit render and you will see the reflection with both setups.
 
Thank you very much

[TomG]

I don't see the reflection at all with the Light.

And I only see the reflection with Shadowcatcher Illuminator enabled with the plane. Images attached. Which version of Corona do you have installed, the latest daily build?

[TomG]

More testing, that was just the lighting not reflection. The normal of the plane is in the wrong direction, so Emit on Both Sides was needed. Still happens that Shadowcatcher Illuminator off, no reflection; on, reflection. New images :)

[Nuno]

More testing, that was just the lighting not reflection. The normal of the plane is in the wrong direction, so Emit on Both Sides was needed. Still happens that Shadowcatcher Illuminator off, no reflection; on, reflection. New images :)

Hoooo dear... my version was out out date I had the "Build timestamp: Jan 29 2018 20:01:23 Version: B1 rc 4 (core 1.7 (hotfix 2)) and was pulling out hairs here on why this is was not working... :(

I just updated (B2 daily May 30 2018 (core 2 DailyBuild May 28 2018)) and everything is working as supposed to be. I am so sorry, for all this :S
I think I have to pay more attention to the new daily releases... Ho god I feel do dumb right now...

Thank you very much for having the patience to clarify things to me :)

Keep it up

Best
Nuno

[TomG]

No worries! I should have asked first thing :)

Here's the scene set up with the two light emitting objects, one casting light but no reflection on the catcher (no light on the objects at all), and one casting light and reflections on the other objects only (no light, nor reflection, on the catcher).

(EDIT - Probably only one needs to be directly visible, but I didn't set that up)

[Nuno]

No worries! I should have asked first thing :)

Here's the scene set up with the two light emitting objects, one casting light but no reflection on the catcher (no light on the objects at all), and one casting light and reflections on the other objects only (no light, nor reflection, on the catcher).

(EDIT - Probably only one needs to be directly visible, but I didn't set that up)

Thank you TomG very much appreciated :)